A vice mayor of a remote town in the southern Philippines was shot and killed Wednesday, the latest politician to be gunned down in a wave of attacks targeting public officials, police said.

Al Rashid Mohammad Ali, the vice mayor of Sapa-Sapa town in the island province of Tawi-Tawi, was travelling in his car in southern Zamboanga City when gunmen on a motorcycle ambushed him, a police report said.

He was shot three times in the body and was rushed to the hospital, but declared dead upon arrival, the report said.

Ali was the fourth local official slain under similar circumstances in recent days.

On Saturday, Alexander Lubigan, a vice mayor in the city of Trece Martires, south of Manila, was killed in his car by gunmen. Two mayors were killed a day apart last week.

The motive for the attacks remains murky. But in at least one case, President Rodrigo Duterte hinted that the killing was linked to drugs.

The latest attack brings to about 16 the number of mayor and vice mayors killed since Duterte became president in 2016 and vowed to cleanse government of narco-politicians.

It was not known, however, if those killed recently were on his list of 150 judges, mayors, police and military personnel the president claimed were involved in the drug trade.

Duterte has often waved the list during public speeches, but has never divulged how he compiled the list.

Rights groups have said that as many as 12,000 people have been killed in the drug war waged by the Duterte administration, although the police have only admitted to some 4,000. Police said those who were killed were suspected drug addicts or dealers who died in shootouts with law enforcement officers.